"...pointed it furiously under Flint's arm at Malfoy's face. A loud bang echoed around the stadium and a jet of green light shot out of the wrong end of Ron's wand, hitting him in the stomach and sending him reeling backwards on to the grass. 'Ron! Ron! Are you all right?' squealed Hermione. Ron opened his mouth to speak, but no words came out. Instead he gave an almightly belch and several slugs dribbled out of his mouth on to his lap."

The Slug-Vomiting Charm[2] (Slugulus Eructo) is a charm that causes the victim to burp up slugs and slime for approximately ten minutes; they may also take on a sallow complexion as a side-effect. It is described as a green jet of light.

In 1992, Ron Weasley attempted to curse Draco Malfoy with this charm after Malfoy referred to Hermione Granger as a "filthy little Mudblood". However, because his wand was broken, the spell backfired causing Ron to curse himself.[3] Ron was then taken inside to Rubeus Hagrid's Hut where he threw up slugs every so often into the basin given him by Hagrid."eat slugs" yelled ron ponting his wand directly at Malfoy, but his spell back fired"

Rupert Grint stated that vomiting slugs was the most challenging scene to film in that movie: "I think coughing up slugs was quite hard. Ron has a scene where he has to cough up these giant slugs. I had this giant slug in my mouth loaded with slime and I spat them out. I think it was plastic. I hope it was plastic."[4]

Despite the challenge, Rupert apparently enjoyed filming the scene: "It was so fun because they had all these different flavours of slug slime. There was chocolate, there was lemon, there was orange, there was peppermint. All these different flavours - they made them taste really nice."[5]